Adapted from J. T. Allen et al., Nature Geoscience, Advance Online Publication (2015)

How El Niño affects your chance of a tornado today

Spring marks peak tornado season for the United States, but the global weather phenomenon El Niño, in which surface waters are abnormally warm in the eastern tropical Pacific, dramatically affects twister numbers. These maps, published online today in Nature Geoscience, contrast springtime tornadoes during El Niño (top) and its mirror, La Niña (bottom), with red denoting enhanced risk and blue showing diminished risk. During La Niña, southerly winds from the Gulf of Mexico ferry warmth and moisture over the central states, spawning thunderstorms and tornadoes there, whereas during El Niño those winds weaken so that the Midwest gets a reprieve while Florida suffers. Right now, a mild El Niño prevails, which suggests that the country's heartland can look forward to a relatively quiet spring.